A conventional art example will be described with reference to FIG. 4 and FIG. 5. FIG. 4 shows a conventional outer magnet type speaker. First magnetic circuit block 10 is made up of yoke 10A, first magnet 10B adhesive bonded to the center of the bottom face of the same, and plate 10C adhesive bonded to magnet 10B. Frame 20 is adhesive bonded on to the top face of plate 10C. The outer circumference of diaphragm 30 is joined to frame 20 via edge 40. The inner circumference of diaphragm 30 is adhesive bonded to voice coil member 50. Voice coil member 50 has coil portion 80. Coil portion 80 is located in the middle of magnetic gap 10D of first magnetic circuit block 10. Further, damper 60 is adhesive bonded to frame 20 and voice coil member 50. Thus, voice coil member 50 is supported for up-and-down movements. On the other hand, FIG. 5 shows a conventional inner magnet type speaker employing a repulsion magnetic circuit. By denoting corresponding parts to those in the speaker of FIG. 4 by like reference numerals, description of the same will be omitted. As shown in FIG. 5, the difference between them is that second magnetic circuit block 70 is provided on the top of first magnetic circuit block 10. Second magnetic circuit block 70 has a second magnet 70A, disposed to generate a magnetic field due to a magnetic flux repulsive to the direction of the magnetic flux from first magnet 10B, and sub-plate 70B. The magnetic flux density in magnetic gap 10D is enhanced by second magnetic circuit block 70. In the case of the speaker shown in FIG. 4, magnetization is not performed on first magnet 10B as a single part. After first magnetic circuit block 10 has been completed through adhesive bonding in an assembling process of a speaker, first magnetic circuit block 10 is magnetized (Magnetization). If first magnet 10B is magnetized prior to adhesive bonding of first magnet 10B with yoke 10A and plate 10C, there arises a problem as follows. First magnet 10B tends to attract yoke 10A and plate 10C each being a magnetic material. As a result, assembling work of first magnetic circuit block 10 becomes difficult. Therefore, first magnet 10B is magnetized after completion of the assembling of first magnetic circuit block 10 through adhesive bonding. On the other hand, a speaker having a repulsion magnetic circuit as shown in FIG. 5 is made up of first magnetic circuit block 10 and second magnetic circuit block 70. Directions of magnetic fields due to magnetic fluxes from first magnet 10B and second magnet 70A are opposite to each other. (That is, they repulse each other.) Therefore, it is impossible to magnetize the two magnetic circuit blocks after they have been adhesively bonded together. Hence, it becomes necessary to adhesively bond the two magnetic circuit blocks together after the first and second magnetic circuit blocks have been magnetized separately. As a result, the manufacturing method involving assembling of such two repulsive magnetic circuit blocks becomes difficult, time-consuming, and hence less productive. The present invention provides a manufacturing method of a repulsion magnetic circuit in which the above mentioned problem is overcome and also provides a manufacturing apparatus for use in the manufacturing method.